1. Field of the Invention
The present invention relates to air spring systems, and, more particularly, to pistons used in rolling lobe air springs.
2. Description of the Related Art
Air spring systems are commonly used in vehicle suspensions, truck cab mountings, and seat suspensions, particularly in heavy vehicles such as over the road trucks and tractors. Such air spring systems typically have large load carrying capacity while retaining excellent isolation of the vehicle or its suspended components from road vibration and harshness due to the compressibility of the air within the air springs.
Construction of air springs for use in air spring systems typically involves the use of a top bead plate, a flexible sleeve, and a lower piston. The flexible sleeve is typically attached to the top bead plate by way of an integrally formed upper mounting bead formed into the flexible sleeve which is then crimped onto the top bead plate. The lower end of the flexible sleeve is also provided with an integrally formed mounting bead, which is captured between the upper surface of the lower piston and a lower end closure. The top bead plate, the flexible sleeve, and the lower end closure together define a spring chamber, which changes in volume as the lower piston articulates, causing the flexible sleeve to roll over itself forming a rolling lobe.
The lower piston of the air spring is often provided with a mounting stud that extends through the piston, the aforementioned lower end closure, and through a vehicle suspension member, such as a trailing arm. The top bead plate is usually attached to some other part of the vehicle structure, such as a mount attached to the vehicle frame. In this way, the air spring provides support of the vehicle mass and load via the frame, suspension, and axles, while providing the necessary isolation from road vibration and harshness.
Pistons for use in such air springs are typically of either formed steel construction, or are molded from plastic. The formed steel variety are usually constructed of deep drawn stampings, often including an outer shell, a base plate, and some inner structure, such as a center column. The molded variety, with which this disclosure is concerned, generally have an outer shell portion, a circular central column, radial webs connecting the outer shell portion and the circular central column, and an upper surface having a recessed upper seating surface configured to receive the lower end closure and the lower bead of the flexible sleeve.
What is needed in the art is way to improve the lateral stiffness and overall strength of the pistons used in air springs, while decreasing overall weight of the pistons and allowing for improved manufacturing by the minimization of manufacturability features such as draft angles.